Much of the world's grass seed is grown in the United States and then exported internationally. Unprocessed grass seed typically includes a significant amount of soil. For example, creeping bentgrass seed can contain around 0.6% soil. For various reasons, some countries impose restrictions on the amount of soil that can be present in grass seed imported into those countries. For example, some countries require that imported grass seed contain no more than 0.01% soil. Australia, Mexico and Japan are examples of countries that have imposed such soil content restrictions.
In the past, faced with the difficulties and inefficiencies of separating the soil and grass seed, exporters have tried coating dirty grass seed to hide the soil instead of actually removing the soil. However, this technique still leaves high soil content in the grass seed in violation of the soil content restrictions. There is therefore a need to effectively remove soil from grass seed to conform with these soil content restrictions prior to shipping the grass seed.